The western part of the municipality lies on the slopes of the Utrecht Hill Ridge and is largely covered by forest and heathlands. The eastern parts lie in the Gelderse Vallei and are mostly agricultural.

The place that is now called Leusden was first mentioned as Villa Lisiduna in a charter in 777. The exact location of that settlement, which is considered to have been a rather extensive farm complex with defenses, is unknown to us. It is possible that the old village of Oud-Leusden once was the location of Villa Lisiduna but excavations in the 1980s have not provided any evidence. However, the church tower of Oud-Leusden is one of the oldest towers in the Netherlands, dating back at least to the 11th century A.D. Close to Leusden is the site of the former monastery Heiligenberg, founded around the year 1000 by bishop Ansfridus of Utrecht, who died here in 1010.

In the 1970s, the agricultural villages of Leusbroek and Hamersveld grew together into a larger, mainly residential town. What once was Hamersveld is now called Leusden-Centrum, now commonly Leusden, and Leusbroek was to become Leusden-Zuid. In the original plans, Leusden was to grow into a town of around 46,000 inhabitants. After the initial expansion there was a growing resistance from the population, so some of the later phases of expansion have been abandoned.